Solder or conductive paste printing stencil holder

ABSTRACT

The mounting of a printing plate (4) takes place with the help of a tie beam (3), which is displaceable with respect to a fixed side (2) of a frame. 
     The connection between the printing plate (4) and the side (2) of the frame or the tie beam (3) consists of a plurality of bolts (17), which are distributed along support bands (16) of the frame side (2) or tie beam (3). 
     The new apparatus allows printing plate (4) to be exchanged without requiring the frame (1) to be removed from the printing bench or the surface to be printed.

The invention relates to an apparatus for solder or conductive pasteprinting, with a frame for the clamping of an etched, milled orlaser-cut printing plate made of metal or plastic, which is secured toat least two oppositely disposed sides of the frame, with the help ofmounting apertures and bolts.

For small formats, this type of apparatus has, up to now, beenconstructed such that the relatively thin printing plate, typically witha thickness of a few tenths of a millimeter, has mounting apertureswhich are threaded upon bolts of the frame, the printing plate thenbeing affixed with beams which are secured to the frame using threadedbolts.

When greater accuracy is required, or for larger formats, the printingplates have been secured to a printing screen which then is cut away inthe region of the printing plate and subsequently mounted into aprinting frame.

Both kinds of connection between the printing plate and the frame aresuch that a change of the printing plate requires a substantial effort,wherein the frame must be removed from the "printing bench", and afterthe replacement it must be again returned to its position.

The aim of the invention is to provide an apparatus in which a change ofprinting plate can be undertaken without each time having to remove theframe and then replace it in position.

According to the invention, this aim is attained in that one of the twoopposed frame sides is constructed as a tie beam which is moveable withrespect to the other side of the frame, the tie beam--in order to mountthe plate, and guided by resiliently mounted guide bolts hingedlyconnected thereto--being displaceable with respect to an abutment whichis located at a fixed distance to the other side of the frame; andfurther in that, along each of the two sides of the frame, and in theworking plane of the frame which receives the plate, a support band forthe plate is provided, the support band having distributed therealong aplurality of bolts provided with heads, by means of which plates ofdifferent thicknesses can, with the help of a spacer shim, be placed inthe working plane and secured to the respective frame sides, wherein thebolts are directed inwardly into the space enclosing the frame.

By the displacement of the tie beam, the printing plate can be tensionedor relaxed. When in the relaxed condition, the new construction makes ispossible for the printing plate with the mounting apertures to beremoved from above, with a new printing plate being inserted, withouthaving to remove the frame from the printing bench.

Advantageously, the support bands are made of thin sheet steel, havingan elasticity which, during printing, makes possible an acceptableplacement of the printing plate on the material to be printed.

In order to prevent the plate from being incorrectly inserted into theframe, it is advantageous to provide, at least for one of the supportbands, a distribution of the bolts which is unsymmetrical with respectto the mid-plane extending perpendicular to the support bands. For thedisplacement of the tie beam it has been found appropriate for the beamto be shaped as a hollow extrusion, in which is inserted, in thelongitudinal direction as a tensioning means, a tube which can be loadedthrough a check valve with a pressure medium, for example, air.Advantageously, the tube has a rectangular section, as well as areinforced forward wall and side walls which, in the relaxed conditionare folded in the manner of bellows.

A quite exact positioning of the printing plate with respect to theframe, and an avoidance of internal tensions and warping of the printingplate, is facilitated by providing, a bolt in the mid-plane of each sideof the frame, with a corresponding mounting aperture in the plate, inorder to provide a centering and position-establishing faculty whereinthe diameters of the bolt and aperture closely match one another, whilethe remaining mounting apertures are formed as oblong openingssurrounding the corresponding bolts with play. A uniform tension overthe entire frame side can be attained if the elongate apertures areprovided with a rectilinear support edge running perpendicular to themid-plane.

The invention will now be more particularly described in terms of anexample embodiment, using the drawings.

FIG. 1, shows, partly in section, a plan view of the frame of the newapparatus;

FIG. 2 is a cross-section taken at II--II in FIG. 1;

FIG. 3 is a plan view of an embodiment of the new printing plate;

FIG. 4 shows, as an enlarged detail from FIG. 1, a plan view of themounting aperture of the plate which lies in the mid-plane;

FIG. 5 shows, likewise enlarged, a plan view of an oblong aperture, and

FIG. 6 is a section taken at VI--VI in FIG. 4.

In a rectangular frame 1 (FIG. 1), assembled from hollow members (FIG.2) which are likewise rectangular in section, a printing plate orprinting screen 4 (FIG. 2) is stretched between a fixed side 2 of theframe on the right and, on the left, a side of the frame which isdisplaceable with respect to the fixed side of the frame 2, and isconstituted by a tie beam 3, the printing plate or screen being onlyschematically represented. The movement of the tie beam 3, beyond whichprojecting arms 5 of the frame 1 extend at both ends, is controlled byguide bolts 6; the latter are mounted on linear bearings 7 in the frame1 and are pressed by springs 8.

The connection between the tie beam 3 and the guide bolts 6 is by way oflink members 9, which are capable of small rotational movements botharound the guide bolts 6 and perpendicular thereto around pegs 10,through which they are connected with the beam 3. The articulated"mounting" of the tie beam allows the latter to accommodate smallimbalances during the stretching of the printing plate 4, and thus toavoid jamming.

The tie beam 3 is a hollow profile (FIG. 2) which is U-shapedcross-section, and in which there is mounted a tube 11 which can beinflated through a check valve 12. The tube has a rectangularcross-section, a reinforced forward wall 13, and bellows-like foldableside walls 14.

When inflated, the tube 11 expands, displaces the tie beam 3 to the leftin FIG. 1, and in this manner stretches the printing plate 4, duringwhich it is supported at its forward wall 13 from an abutment member 15which is integrated into the frame 1 parallel to the fixed side 2 of theframe.

In the corners of the frame 1 there are threaded bores 22 into whichnon-illustrated micrometer screws can be provided, with which the heightof the frame relative to the printed surface can be adjusted.

Provided on the side 2 of the frame and on the tie beam 3 are respectivesupport bands 16 located in the working plane of the printing plate 4. Aplurality of T-shaped bolts 17 each having a stem and a head aredistributed along each support band 16. As FIG. 1 shows, thedistribution of the bolts 17 along one support band 16 is asymmetrical.By virtue of such distribution, it can be ensured that the printingplate 4, which has correspondingly arranged and distributed attachmentapertures 18 (FIG. 3), can be attached to the frame 1 in only a singleposition.

The attachment of the printing plate to the support bands 16 is carriedout with the help of wedge shaped spacer shims 19, which have recesses20 which conform in position and size to the bolts 17. With its wedgeshape, which makes possible the securement of printing plates 4 ofdiffering thicknesses, the spacer shims 19 when inserted grip theT-shaped bolts 17 from beneath, and connect the printing plate 4 to thesupport bands 16 (FIG. 6). At the same time, the spacer shims 19 holdthe plate 4 in the working plane.

As seen in FIG. 3, the printing plate 4 is provided with two differentmounting apertures 18: in the mid-plane 21 are located pear-shapedmounting apertures 18', of which the neck 23 is matched to the diameterof the corresponding bolts 17; moreover, the neck 23 is centred in themid-plane 21. The mid-plane 21 can thus serve as a null-line for thex-coordinate of an xy-coordinate system (not illustrated) with which theposition of cardinal points on the printing plate can be exactlyestablished. The null-line of the corresponding y-coordinate (also notillustrated) lies along the mid-line of the printing plate which isperpendicular to the plane 21.

The remaining mounting apertures 18 are of oblong form, in which thebolts 17 can freely move in the lateral direction. By this means it ispossible to avoid undue tension and warping when tightening the printingplate. As shown in FIG. 5, the edges 24 of the oblong apertures 18,which lie against the bolts 17 when the printing plate is tightened,have a rectilinear configuration. The latter ensures an evendistribution of the tension forces along the whole length of theprinting plate 4.

I claim:
 1. An apparatus for solder or conductive paste printingincluding a frame defining a working plane and enclosing a space formounting one of an etched, milled and laser-cut printing plate made ofone of metal and plastic, said frame having two opposite sides, aplurality of mounting bolts and a plurality of apertures the printingplate being secured to at least said two opposite sides of the framewith said plurality of mounting apertures and said plurality of mountingbolts,characterized in that, one of the two sides of the frame is a tiebeam and includes means for moving the tie beam with respect to theother one of two sides, the tie beam being guided by resiliently mountedguide bolts and pivotally connected to said guide bolts, an abutment issecured to and located at a fixed distance from the other side of theframe said tie beam being displaceable with respect to said abutment, asupport band for the plate provided along each of the two frame sidesfor the plate, the support band being in the working plane of the framewhich receives the plate, there being, distributed along the supportband, a plurality of said mounting bolts provided with heads forreleaseably securing plates of differing thicknesses in the workingplane, said mounting bolts being fixedly secured to the respective frameside, the mounting bolts extending inwardly from the working plane intothe space enclosed by the frame, the plate being removable from saidframe via said mounting bolts.
 2. An apparatus according to claim 1,characterized in that, in at least one of the support bands the mountingbolts are distributed asymmetrically with respect to a mid-plane of theframe extending perpendicular to the support bands.
 3. An apparatusaccording to claim 1 characterized in that the support bands are steel.4. An apparatus according to claim 1 wherein the tie beam is a hollowextrusion extending in an elongation direction along one of said sides,in which extrusion a flexible tube, adapted to be loaded with a pressuremedium through a check valve, is inserted in the elongation directionfor tensioning the plate when the tube is pressurized.
 5. An apparatusaccording to claim 4, characterized in that the tube has a relaxedcondition and an expanded tension inducing condition, the tube furtherhas a rectangular section and a reinforced forward wall and in therelaxed condition has bellows-like folded side walls.
 6. An apparatusaccording to claim 1, characterized in that in the mid-plane of eachframe side a mounting bolt and in the plate a corresponding mountingaperture are included having closely matching diameters for centeringand position-establishing of said plate relative to said frame, whereasthe remaining mounting apertures are elongated surrounding thecorresponding mounting bolts with clearance.
 7. An apparatus accordingto claim 6, characterized in that the elongated apertures each havestraight abutment edges running perpendicular to the mid-plane.
 8. Theapparatus of claim 1 further including a spacer shim for selectivelyaltering the space between the support band and said mounting bolt headsfor closely receiving a printing plate of a corresponding thicknesstherebetween.
 9. The apparatus of claim 8 wherein the shim is taperedfor selectively releasably clamping said plates of differing thicknessesto said support band and bolt heads.
 10. A printing plate for solder orconductive paste printing, for use in a solder or paste applyingapparatus including a plurality of mounting bolts extending in adirection along opposite frame sides, said plate comprising at least twoopposing sides with edges, said plate having first mounting aperturesalong the edges of at least said two opposing sides, both said edges ofthe plate being a second corresponding elongated centering mountingaperture for the positioning and centering of the plate in theapparatus, said second elongated centering mounting aperture decreasingin width toward the corresponding plate edge, said first and secondapertures receiving one of said mounting bolts for releasably securingthe plate to said frame sides.
 11. A printing plate according to claim10 wherein the frame sides have edges, a different portion of the firstapertures corresponding to a different frame side, the first aperturescomprising elongated openings and have a substantially straight edgeextending in a direction along the edge of the corresponding frame side.12. A printing plate according to claim 10, characterized in that thefirst and second mounting apertures are arranged along a frame edgeasymmetrically with respect to a mid-plane of that frame side.
 13. Anapparatus for solder or conductive paste printing with a printing platehaving a plurality of apertures, said apparatus comprising:a framehaving at least two opposite sides defining a working plane andenclosing a space, one of said sides comprising a hollow tie beammoveable relative to the other side; a flexible tube in the tie beamhaving means for being pressurized for tensioning the plate, said tubehaving a rectangular section in the pressurized state and bellows-likefolded sides in the relaxed state: resilient means including guide meansfor resiliently guiding the tie beam relative to the frame other side:means for pivotally connecting the resilient means to said tie beam; asupport band connected to each of said sides for receiving said printingplate in said working plane: and a plurality of plate mounting boltsdistributed along each said support band adapted to mate with andreceive said plate apertures, said bolts having heads spaced from saidsupport bands for releaseably receiving plates of differing thicknessestherebetween in the frame working plane, said bolt heads extending intosaid space.
 14. The apparatus of claim 13 wherein one of said tube sidesincludes a reinforced wall adjacent to said tie beam and secured to theother side.
 15. The apparatus of claim 13 further including shim meansadapted to provide different spacings between said bolt heads andcorresponding support band to closely receive corresponding differentthickness plates between the corresponding support band and heads. 16.The apparatus of claim 13 wherein said means for hingedly securingincludes means for hingedly securing the resilient means for rotationabout two orthogonal axes.
 17. The apparatus of claim 13 wherein one ofsaid tube sides includes a reinforced wall adjacent to the tie beam andsecured to the other of said sides, said tube expanding against saidwall in response to said pressurizing for displacing said tie beamrelative to the wall in a tensioning direction relative to the otherside.
 18. An apparatus for solder or conductive paste printing with aprinting plate having a plurality of plate securing apertures, saidapparatus comprising:a frame having at least two opposite sides defininga working plane and enclosing a space, one of said sides comprising ahollow tie beam moveable relative to the other side; a flexible tube inthe tie beam adapted to be pressurized for tensioning the plate, saidtube having a rectangular section in the pressurized state andbellows-like folded sides in the relaxed state: resilient meansincluding guide means for resiliently guiding the tie beam relative tothe frame other side; means for hingedly connecting the resilient meansto said tie beam; a support band connected to each said sides forreceiving said printing plate in said working plane; a plurality ofplate securing bolts distributed along each said support band adapted tomate with and receive said plate apertures, said bolts having headsspaced from said support bands for releaseably receiving plates ofdiffering thicknesses therebetween in the frame working plane, saidbolts extending into said space; and a mounting positioning boltcentrally located on each frame side for receiving a correspondingcentrally located positioning aperture in said plate, the positioningbolt and aperture having closely matching diameters for centering andpositioning the plate relative to the frame, said securing aperturesbeing larger than the corresponding securing bolts received thereby forproviding play therebetween.
 19. The apparatus of claim 18 wherein saidresilient means comprises a pair of like spaced resilient guide meansincluding guide rods at opposite ends of said tie beam, said means forhingedly connecting including articulated means rotatable about twoorthogonal axes for hingedly securing each said spaced resilient guidemeans to said tie beam at said opposing ends of the tie beam.
 20. Theapparatus of claim 18 further including tapered shim means adapted toprovide different spacings between said bolt heads and correspondingsupport band to receive corresponding different thickness platestherebetween.